Photographic color reproduction process



P 15, 1953 L. M. CONDAX 2,652,327

PHOTOGRAPHIC COLOR REPRODUCTION PROCESS Filed July 19, 1951 Fig.

C y Z UNOYEO,FLA$HED AND REVERSED s wm/v RELIEF 0 UNDYED, FLAS/IED A/VD RE I/ERSED CYA/V RELIEF MAGE/WZI DYED PRIMARY REL/EF Fig 3 4/ /Au/v0r0 FLASHED 4N0 REVERSED S M MAGE/W'A REL/5F CORRECTED MAGENTA REL IEF I LOU/S M. C U/VDAX CORRECTED INVENTOR- YELLOW RELIEF Y W T TEQ EE \BY W r p c 41W ATT') a 467 Patented Sept. 15, 1953 PHOTOGRAPHIC COLOR REPRODUCTION PROCESS Louis M. Condax, Rochester,

Eastman Kodak Company,

N. Y., assignor to Rochester, N. Y., a

corporation of New Jersey Application July 19, 1951, Serial No. 237,680

Claims.

This invention relates to color photographic processes and particularly to a method of producing color correction of colored photographic images produced by dye imbibition.

It is well known that the dyes or coloring material used to form colored images in three-color photographic processes undesirably absorb light in the region of the spectrum where the highest transmission is desired, as is more fully discussed in Evans U. 5. Patent 2,203,653, Evans and Hanson U. S. Patent 2,371,746 and elsewhere.

In dye imibibition processes of color photography there is produced a number, usually three, of color separation records in the form of relief images which are dyed to the requisite colors and these are used to produce superimposed dye images giving a subtractively colored multicolor image. Usually the three color separation relief images are respectively a positive record of the blue which is dyed yellow, a positive record of the green which is dyed magenta and a positive record of the red which is dyed cyan. These may be bound in superimposition or the dye images transferred to a single support in superimposition.

For convenience in the present specification, the reliefs which are used directly in this way for forming the superimposed images will be referred to as primary reliefs, since the invention employs further reliefs which are not so used directly and these will be referred to as secondary reliefs.

One object of my invention is to provide a method of modifying the amount of dye absorbed in one or more of a set of dyed color separation relief images to five color correction for unwanted absorption. Another object is to provide a method of modifying the amounts of dye absorbed in one or more of a set of dyed color separation relief images to give tone correction. A further object is to provide a method of modifying the amounts of dye absorbed in one or more of a set of dyed color separation relief images to give both color and tone correction. Other objects of my invention will become apparent from the following description.

In these processes the resultant composite dye images show the well known effects of unwanted light absorption of the dye images. In previously described methods of masking, a blackand-white negative image is registered with the original transparency prior to making the separation negatives or a black-and-white positive is bound with one or more separation negatives themselves. In both of these methods the cordye in the magenta relief is rections are produced prior to making the printing matrices. In the method of the Gresham U. S. patent application Serial No. 54,328, filed October 13, 1948, now U. S. Patent 2,600,756, granted June 17, 1952, the corrections are carried out on the dyed (primary) reliefs by using an undyed (secondary) relief to imbibe a portion of the dye from the primary relief before the image is transferred to paper. The image of the secondary relief is, of course, laterally reversed. The dye remaining in the primary relief is then transferred to form a part of the final image. The method is especially advantageous at times when masking by the standard procedure is not feasible. It is applicable to largescale production of still or motion-picture prints in color. A preferred procedure is as follows: A. contrast-reducing negative mask is first produced from the original transparency as described in the booklet Masking for the Dye Transfer Process published by Eastman Kodak Company, Rochester, New York, 1950. With this mask in place on the transparency, the separation negatives are next made in the usual manner. The black-and-white mask at this stage controls the relative brightness of certain colors but does not correct the hue shift. From the red filter negative of this set, a normal cyan printing primary relief is now exposed. Then the red filter negative is reversed and used to print a secondary relief which serves as the colorcorrecting mask. The magenta and yellow primary relief matrices are next printed with approximately 20 percent increase over the normal exposure. The three primary reliefs are then dyed as usual but the masking secondary relief is left undyed. The cyan is transferred first in the usual way. Then, while the cyan dye is transferring, the magenta image is brought into register and in contact with the undyed masking relief from the red filter negative. A portion of the magenta dye gradually transfers from the magenta relief into the undyed masking relief until equilibrium is established. The remaining now transferred to the paper bearing the cyan image. The dye is removed from the masking relief by Washing. The same masking relief may be used to correct the yellow printing relief. However, much better color correction is effected if a second masking relief is made from the green filter negative, especially for correcting the yellow primary relief. This procedure improves the green colors.

In working with this process, the possibility of 'fi-ash exposures and to place certain improvements became evident. For example, if the masking matrix was given a small amount of flash exposure in addition to the regular exposure through the negative, the highlight portions of the relief images were thicker and of lower gradient, and the amount of dye the mask removed from the highlights of the printing relief was greater. Thus the flash exposure has the effect similar to that of an additional highlight mask which increases the tone separation in the highlights with the practical result that the unwanted highlight stain or-density commonly associated with these processes is thereby reduced. It was found that the amount of flash exposure can be varied from about 5 to /5 of the total exposure, depending upon the amount of tone control desired in the toe of the characteristic curve. When the flash exposure is used for the masking of secondary reliefs, the cyan primary relief, like the magenta and yellow printing primary reliefs, must be given about a 20 percent increase in exposure and then reduced to obtain three printing primary reliefs with characteristic curves of the same shape. This is an advantage since all three'images can then be overprinted to the same degree. The only extra time required is the time required to give the the red filter masking secondary relief in contact with the cyan printing primary relief to reduce .the contrast of the cyan image.

-In practica it has been found that the pin registration system is most convenient for this meth- 0d of masking. However, pre-registered matrices can be combined on a transfer blanket by first placing the undyed mask on itface down until it is incontact with the buttons and then rolling it down on the register board. The blanket 'is now carefully lifted so as to leave the mask on the register board without disturbing its location and thedyedmatrix is 'placed'face up on the blanket and rolled in contactwith the mask. A portion of the dye is now removed from the printing primary relief by the undyed mask until an equilibrium is established in two or three minutes. The two matrices are now lifted-and peeled apart, and the matrix bearing the corrected image is placed in one percent acetic acid solution for a few seconds prior to transferring. The dye is then washed out of the masking relief to make .it ready for use again. If two transfer blankets are available, the dye removal for the-color correction'of the second image can be carried out simultaneously with the transfer of the dye from the first image.

Additional improvements-can .be made in controlling the contrast of the primary reliefs in relation to the masking.secondary reliefs so that finalprint contrast is satisfactory. This is done by printing the mask .as light as possible so that the highlight detail is-at a minimum, and using the tanning developer at the lowest contrast (one part of Solution A and one part of Solution 3) for the masking reliefs only.

A Solution Pyrogallol grams 6 Hydroquinone do v3 Elon do 2 Citric acid do 3 Water to Z1 liter.

BSoZufion Potassium'carbonate gm 200 Potassium bromide (10% solution) cc 20 'Water to 1 liter.

The printing reliefs, on the other hand, are

age may be increased by increasing the acidity of the dye solutions if necessary. An improved method for controlling the contrast of the matrix the method described.

may be substituted for This method employs a further increase of the quantity of .Solution B in the tanning developer to increase contrast.

Accordingly,.by my invention correction for unwanted absorption of a color by a dye in one of the set of dyed color separation relief images is obtained by removing dye from the dyed, primary reliefimage which records the color .unwantedly absorbed and which relief has unwanted highlight density, by bringingit into contact and .in register with an undyed secondary relief .image whichis. arecord of the dyed relief image bearing the saidunwanted absorption and which undyed relief image has the highlight .densityincreased by uniform exposure to light. For example, undesired absorption of blue light by a magenta dye (in a green record color separation relief image) may be corrected .by pressing the blue record primary relief (dyed yellow). into contact with an undyed green record secondary relief which has been given the hash exposure mentioned. The result is that tone correctionof the yellow relief is also eifectedsincethe-undyed relief takes density out of the highlight areas of the yellow relief. It. is apparent that the undyed green record secondary relief should be laterally reversed compared with the dyed primary relief image. This method may be used for the correction of unwanted absorption ofone or. more colors by one or more dyes in the same set of relief images. by performing contacting operations between the appropriate dyed primary and undyed secondary reliefs according to thezinvention.

.As a further illustration of the invention, if it is desired to correctv for the undesired blue absorption of the cyan dye and to correct. for the tone .of the yellow primary .relief, ,a secondary relief is made through the same colored filteras that used for making the cyan image and giving theadditional flash'exposure, and this-secondary relief. is squeegeedin register with the yellowdyed primary relief whereuponthe yellow .dye is shared between the two reliefs in accordance with the relative dye imbibition properties of the two reliefs at each point of the image. .In some cases theyellow dye may be introduced only by .dyeing first the secondary relief, in which case. the. dye is shared although the intensities obtained .at everypoint in the primaryrelief will notusually be the same as would be obtained by dyeing only the primary relief, because :the reliefs are not usually left in contact for the long time which Would be necessary to enable-the dyedistribution to reach equilibrium.

An example illustrating-the making ofa threecolor imbibition picture in which there is obtained correction for the undesired blue absorption of the magenta dye, the undesired green absorption of the cyan dye and undesired dye density inqthe highlights of the cyan, magenta and yellow dyeimages, is as follows:

A set of blue, green and .red color separation negatives is provided in the usual manner. From each of these negatives is made a gelatin primary relief image using about percent more than the normal exposure. These reliefs can be checked for balance and density after dyeing them up in the respective subtractive colored dyes. When the primary set of reliefs is satisfactory, an extra secondary relief is made from each of the red and green record separation negatives, giving them exactly the same treatment as for those of the primary set, except that the negatives are turned over in the enlarger so that the secondary reliefs are laterally reversed with respect to the primary reliefs and each is given a flash exposure of about to of the total exposure time. The three primary reliefs are now dyed up in baths of cyan, magenta and yellow dyes. When this dyeing is complete, the dyed reliefs are rinsed in dilute acetic acid solution (for instance, one percent, depending upon the dyes used) and the cyan primary relief is squeegeed down in register face to face with the laterally reversed red record secondary relief. As a result, dye is taken out of the primary relief wherever the secondary relief image areas coincide and proportionally more dye is taken out of the highlight areas than elsewhere. After about five minutes, the cyan dye remaining in the primary relief is then imbibed on to mordanted paper. The red record secondary relief is then washed out and squeegeed face to face with the magenta-dyed primary relief. After about five minutes, the magenta dye image remaining in the primary relief is transferred in register to the cyan image on the mordanted paper. Similarly, the yellow-dyed primary relief is squeegeed face to face with the green record secondary relief and after about five minutes the remaining yellow dye image is transferred from the primary relief to the mordanted paper. As a result, a color-corrected subtractively-colored imbibition print is obtained in which the extreme highlight regions (particularly the whites) are substantially free of cyan, magenta or yellow dye density.

The accompanying drawings illustrate my invention by showing in enlarged cross-sectional view the appearance at different stages of typical elements utilized in correcting the mentioned primary reliefs.

In the drawings, Figs. 1-3 show the cyan, magenta and yellow dyed primary reliefs (Cp, Mp and Yp) being corrected by transfer of dye therefrom to the undyed laterally reversed flashed secondary reliefs Cs, Cs and Ms, respectively, as described in the example immediately above. As a result, the undyed reliefs remove dye from the dyed primary reliefs in both the high and low density regions, thus undesirable dye is removed from the highlight regions as desired. Figs. 4-6 illustrate the appearance of the primary reliefs Cp, Mp and Yp after contact with the undyed reliefs, from which it can be seen that the overall dye density of the reliefs has been reduced including the dye density in the highlight areas.

It is well known that in multicolor processes including those employing color correction, it is very desirable to so balance the over-all quantities of dye employed that at least neutral grays are reproduced (i. e. for visual examination) with a reasonable accuracy. In the present process also, the concentration of dyes employed should be chosen with this in mind.

It i apparent that any of the dyes usually employed in dye imbibition processes may be used in my invention, although the optimum time of contact and the concentration employed may vary slightly from dye to dye as described above. The type of gelatin employed in the relief images or layers will also affect the optimum time of contact, soft or untanned gelatin reaching equilibrium more rapidly than hard or tanned gelatin in the manner well known to those skilled in the art.

One advantage of the process is that it is not necessary to know in advance that color correction masking is to be applied since any existing separation negatives of normal contrast are suitable. It is even possible to make the secondary reliefs after a normal uncorrected dye transfer print has been made if it is considered that the result is unsatisfactory without correction and then a new. corrected print can be made. Another advantage is that the process requires little or no more knowledge or skill on the part of the operator than the making of uncorrected three-color dye imbibition prints, and it is not necessary to do the somewhat laborious work of making correcting masks which require accurate densitometric control.

The present invention can be applied to produce correction of screen negatives for use in halftone block making or photolitho plate making. The procedure is to make separation negatives from which separation positive reliefs are made and in this case the correction is made in a somewhat similar manner to that described above for dye transfer print making, except that it is unnecessary to dye the positive reliefs up in different colors. For this purpose it would be sufiicient to dye all the positive reliefs in a yellow dye since we are only concerned with the densities of the reliefs to blue light when screen negatives are made therefrom on blue-sensitive plates. Therefore, it is only necessary to make a set of three-color positive primary reliefs and two secondary reliefs in exactly the same way as described above, except that all dye used is yellow dye. If desired, a color print can be made from the same reliefs as a guide in subsequent operations, and this may often be a very big advantage to photomechanical workers when they are faced with the problem of reproducing "transparencies. As the yellow-dyed reliefs are to be used as positives, it is desirable to remove any silver therefrom. Alternatively, the dye from a set of reliefs can be transferred to a set of mordanted plain gelatin-coated plates.

The secondary reliefs used in the foregoing halftone or photolitho process may also be used for making a black printer as follows: Two secondary reliefs are made and used as in the foregoing halftone or photolitho process, 1. e. with the use of a yellow dye only, and also a third secondary relief is made as a laterally reversed blue record positive relief and the yellowdyed red record positive primary relief is squeegeed face to face in register therewith. There are then obtained three secondary reliefs; where a primary color was present in the original, dye will only be transferred to one of the secondary reliefs; and where a subtractive color was present in the original, no dye will be transferred to the secondary reliefs. The three dyed secondary reliefs can then be superposed, or dye from all three can be transferred to another (mordanted) layer in register. In either case, the composite image so obtained can be used as a printer by means of light so chosen in color in relation to the dye, as to give a gamma 7 suitable for a black printer for use-with the three corrected yellow-dyed positive primary reliefs.

It will be apparentthat since the proper working of.the present invention depends upon the ability of the primary relief to share dye with another layer (secondary relief), it is important thatthese layers should not, during the sharing process, contain a mordant for the dye which is to be shared. In the application of the invention either to color correction or tone correction or: both, the amount of dye remaining in the primary relief must be sufficient to allow the dye image to be used for the production of the final three-color picture.

What ,I claim is:

l.- The method of making a color and tonecorrected photographic print by means of three dyed color separation reliefs, whose dye images are superimposed to give a print, at least one of which, dye images has both wanted and unwanted spectral absorption, which com rises correcting for the unwanted light absorption of one of said dye images having wanted and un wanted spectral absorption and at the same time correcting for unwanted highlight density of another of said dye images, by removing dye from the dyed relief which records the color which is unwantedly absorbed, by bringing it into contact and in register: with an undyed reiief containing the areas of unwanted absorption, the higl light density areas of which have been increased by uniform light exposure, and then combining thecorrected relief thus obtained, with the re mainder of said three-color separation reliefs'to producea color picture.

2. The method of making'a color and tonecorrected photographic print by means of three color separation reliefs dyed yellow, magenta and cyan respectively, whose dye images are su erimposed to give a print, which comprises correcting for the unwanted blue light absorption of the-magenta dye image and for the unwanted highlight density of the yellow dye image, by removing dye from the yellow-dyed relief by bringing it into contact with an undyed relief which is a green separation record, the highlight density areas of which have been increased by uniform light exposure, and then combining the corrected relief image thus obtained with the remainder of said. three color separation relief images. to produce a color picture.

3. The method of making a. color and tonecorrected photographic print by means of three color. separation reliefs dyed yellow, magenta and cyan respectively, whose dye images are superimposed to give a print, which comprises removing dye from the magenta-dyed relief by bringing it into contact with an undyed relief which is a red separation record, the highlight density areas of which have been increased byuniform light exposure, and then combining thecorrected relief image thus obtained with the remainder of said three color separation relief images to produce a color picture.

4. The method of making a color and tone corrected photographic print by meansof threecolor separation reliefs dyed yellow, magenta and cyan respectively, whose dye images are. superimposed to give a print, which comprises correcting for the unwanted blue light absorp-- tion of the magenta dye image and for the unwanted highlight density of the yellow and magenta dye images, by removing dye from the. yellow and magenta-dyed reliefs by bringing theyellow relief into contact with anundyed green separation relief and the magenta relief into contact with an undyed red separation relief, the highlight density areas of said undyed reliefs having been increased by uniform light exposure, and then combining the corrected dye images thus obtained with the cyan dye image toproduce a color picture.

5. The method of making a' color andtonecorrected photographic print by means of three color separation reliefs dyed yellow, magenta and cyan respectively, whose dye images are superimposed to give a print, which comprises correcting for the unwanted blue light absorption of the magenta dye. image and for the un-- wanted green light absorption of thecyan dye image as well as for unwanted highlight density.

of all of said dye reliefs, by removing dye from.

said reliefs by bringing the cyan relief into contact with an undyed red separation relief, the magenta relief into contact with an undyed red separation relief and the yellow relief into contact with an undyed green separation relief, the

highlight densities of each of said undyed reliefshavin been increased by uniform light exposure, and then combining the corrected cyan, magenta and yellow dye images thus obtained to produce a color picture.

LOUIS M. CONDAX.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. THE METHOD OF MAKING A COLOR AND TONECORRECTED PHOTOGRAPHIC PRINT BY MEANS OF THREE DYED COLOR SEPARATION RELIEFS, WHOSE DYE IMAGES ARE SUPERIMPOSED TO GIVE A PRINT, AT LEAST ONE OF WHICH DYE IMAGES HAS BOTH WANTED AND UNWANTED SPECTRAL OBSORPTION, WHICH COMPRISES A CORRECTING FOR THE UNWANTED LIGHT ABSORPTION OF ONE OF SAID DYE IMAGES HAVING WANTED AND UNWANTED SPECTRAL ABSORPTION AND AT THE SAME TIME CORRECTING FOR UNWANTED HIGHLIGHT DENSITY OF ANOTHER OF SAID DYE IMAGES, BY REMOVING DYE FROM THE DYED RELIEF WHICH RECORDS THE COLOR WHICH IS UNWANTEDLY ABSORBED, BY BRINGING IT INTO CONTACT AND IN REGISTER WITH AN UNDYED RELIEF CONTAINING THE AREAS OF UNWANTED ABSORPTION, THE HIGHLIGHT DENSITY AREAS OF WHICH HAVE BEEN INCREASED BY UNIFORM LIGHT EXPOSURE, AND THEN COMBINING THE CORRECTED RELIEF THUS OBTAINED, WITH THE REMAINDER OF SAID THREE COLOR SEPARATION RELIEFS TO PRODUCE A COLOR PICTURE. 